Despite the considerable advances in the understanding of the structure of the T cell antigen receptor in recent years, the relationship of structure to function remains obscure. To date two polypeptides appear to be common to all cytotoxic T (Tc) cell and helper T (Th) cell receptors. These are referred to as Alpha and beta suunits of the T cell receptor. Class I MHC restricted Tc cells have an additional T cell receptor-like sub-unit referred to as Gamma. Although antibodies have been prepared to demonstrate the presence of the TAlpha and TBeta polypeptides in T cells, no such reagent exists for the study of the still putative TGamma polypeptide. So far there is nonly evidence for T transcripts. The proces swhereby T cells acquire MHC restriction, the dual recognition specificity of self MHC with foreign antigen, is not understood. The thymus appears to be involved in the repertoire formation, at least for class II MHC restricted T cells. It is less clear for class I MHC-restricted T cells. We have developed an experimental system to investigate these questions. We have maintained in culture for several years a series of Tc lines, some of which are alloreactive, and others specific for SV40 antigens and restricted to a particular H-2 haplotype. One of the Tc lines, B6.cl4, responds to SV40-transformed H-2Kb-bearing cells. We have generated 4 anti-idiotypic monoclonal antibodies directed against the T cell receptor of B6.c14. Furthermore, we have isolated representative cDNA and genomic clones for TAlpha, TBeta and TGamma from B6.cl4. By the technique of protoplast fusion, we will transfer these cDNA clones under the control of RSVLTR (Rous sarcoma virus long terminal repeat) promoter into varius T cell lines and determine the combination of TAlpha, TBeta and TGamma that reconstitutes the antigen/MHC specificity of B6.cl4. Using H2Ld promoter, the cDNAs will also be subcloned into retroviral vectors in order to introduce this information into mouse bone marrow cells. We will also use the genomic clones under the direction of their own promoters to construct transgneic mice. These animal systems will allow us to study the ontogeny of T cell receptors and especially to investigate the putative role of TGamma in T cell MHC restriction.